Thursday, November 29, 2007

What Is Evolution?

Greg Laden has just posted this video on his blog [Evolution ... Its for real]. I assume Greg endorses the definition of evolution in the opening minutes.

On Tuesday and Wednesday evenings I gave lectures on Evolution Is a Theory and a Fact. The first part of the lecture was devoted to explaining What Is Evolution. Here's the minimal scientific definition of evolution.

Evolution is a process that results in heritable changes in a population spread over many generations.

I explained to the audience that the definition of evolution has to be neutral with respect to mechanism. Evolution could occur by Lamarckian or Darwinian mechanisms, or something else entirely different.

The purpose of a definition is to define what we mean by the word. If we were to define evolution as that form of change caused by meiotic drive then change by natural selection wouldn't be evolution. How silly is that?

It's just as wrong to define evolution in terms of natural selection. That means random genetic drift is not evolution, by definition. Is that right?

The opening screen of the video states "The world is full of misinformation." The second screen says, "Many of those who claim evolution is wrong have no understanding what evolution really is."

This is exactly how I begin my talk. However, from that point on my lecture diverges considerably from the video that cdk007 created. Do you agree with the definition in the video? (Natural selection + time = EVOLUTION)

10 comments
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I wonder if this isn't a case of an equation being correct but not definitive. For example, 1 + 3 = 4 is correct. But 4 = 1 + 3 is too limited, because 2 + 2 = 4 also.

So, Natural selection + Time = Evolution is not incorrect, because if you add those two you will get evolution as you define it. But Evolution = Natural selection + time would make me cringe, as it does for you. The question is, which did the video's producer intend?

I think a good definition of "heritable" is needed for that defition of evolution to be adequately understood. It is not as simple as some would think. Mst people would siomple equate heriyable with genetic, and take the defintion as a rehash of Dobzhansky's defintion.

Plus, I myself think that not any population frewuency change is an evolutinary change, specially if no new organic, phenotypic change is involved. I don't think that will always be evolution, but according to your dfinition, it always is.

I am just noting that it was never clearly offered as a definition per se, that an obvious alternative interpretation presents itself, and that the model included exactly as much drift as selection. I don't have any particularly strong opinion either way beyond that. Overall, I think the simulation is useful, but I agree that they should take special steps to avoid the appearance of defining evolution as natural selection. Unless, of course, that is how they define it, in which case you and I will be on exactly the same side.

Larry Moran seems to oppose "Natural Selection + time = evolution" because it leaves out sampling error (genetic drift).Does this alternative definition satisfy you Larry?Natural selection superimposed on Variation (mutations, variation produced by selective mating and by sampling error) + time (generations of selection) = ADAPTIVE evolution.Darwin replaced the theological argument from "design" to God with a scientific argument from "design" (adaptations) to the natural processes that produce the adaptations.The really "interesting" questions for most of us are the theories about the natural processes that bring about the adaptive evolution of "designs" rather than questions about the role of chance in evolution.

Laurence A. Moran

Larry Moran is a Professor Emeritus in the Department of Biochemistry at the University of Toronto. You can contact him by looking up his email address on the University of Toronto website.

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Quotations

The old argument of design in nature, as given by Paley, which formerly seemed to me to be so conclusive, fails, now that the law of natural selection has been discovered. We can no longer argue that, for instance, the beautiful hinge of a bivalve shell must have been made by an intelligent being, like the hinge of a door by man. There seems to be no more design in the variability of organic beings and in the action of natural selection, than in the course which the wind blows.Charles Darwin (c1880)Although I am fully convinced of the truth of the views given in this volume, I by no means expect to convince experienced naturalists whose minds are stocked with a multitude of facts all viewed, during a long course of years, from a point of view directly opposite to mine. It is so easy to hide our ignorance under such expressions as "plan of creation," "unity of design," etc., and to think that we give an explanation when we only restate a fact. Any one whose disposition leads him to attach more weight to unexplained difficulties than to the explanation of a certain number of facts will certainly reject the theory.

Charles Darwin (1859)Science reveals where religion conceals. Where religion purports to explain, it actually resorts to tautology. To assert that "God did it" is no more than an admission of ignorance dressed deceitfully as an explanation...

Quotations

The world is not inhabited exclusively by fools, and when a subject arouses intense interest, as this one has, something other than semantics is usually at stake.
Stephen Jay Gould (1982)
I have championed contingency, and will continue to do so, because its large realm and legitimate claims have been so poorly attended by evolutionary scientists who cannot discern the beat of this different drummer while their brains and ears remain tuned to only the sounds of general theory.
Stephen Jay Gould (2002) p.1339
The essence of Darwinism lies in its claim that natural selection creates the fit. Variation is ubiquitous and random in direction. It supplies raw material only. Natural selection directs the course of evolutionary change.
Stephen Jay Gould (1977)
Rudyard Kipling asked how the leopard got its spots, the rhino its wrinkled skin. He called his answers "just-so stories." When evolutionists try to explain form and behavior, they also tell just-so stories—and the agent is natural selection. Virtuosity in invention replaces testability as the criterion for acceptance.
Stephen Jay Gould (1980)
Since 'change of gene frequencies in populations' is the 'official' definition of evolution, randomness has transgressed Darwin's border and asserted itself as an agent of evolutionary change.
Stephen Jay Gould (1983) p.335
The first commandment for all versions of NOMA might be summarized by stating: "Thou shalt not mix the magisteria by claiming that God directly ordains important events in the history of nature by special interference knowable only through revelation and not accessible to science." In common parlance, we refer to such special interference as "miracle"—operationally defined as a unique and temporary suspension of natural law to reorder the facts of nature by divine fiat.
Stephen Jay Gould (1999) p.84

Quotations

My own view is that conclusions about the evolution of human behavior should be based on research at least as rigorous as that used in studying nonhuman animals. And if you read the animal behavior journals, you'll see that this requirement sets the bar pretty high, so that many assertions about evolutionary psychology sink without a trace.

Jerry Coyne
Why Evolution Is TrueI once made the remark that two things disappeared in 1990: one was communism, the other was biochemistry and that only one of them should be allowed to come back.

Sydney Brenner
TIBS Dec. 2000
It is naïve to think that if a species' environment changes the species must adapt or else become extinct.... Just as a changed environment need not set in motion selection for new adaptations, new adaptations may evolve in an unchanging environment if new mutations arise that are superior to any pre-existing variations

Douglas Futuyma
One of the most frightening things in the Western world, and in this country in particular, is the number of people who believe in things that are scientifically false. If someone tells me that the earth is less than 10,000 years old, in my opinion he should see a psychiatrist.

Francis Crick
There will be no difficulty in computers being adapted to biology. There will be luddites. But they will be buried.

Sydney Brenner
An atheist before Darwin could have said, following Hume: 'I have no explanation for complex biological design. All I know is that God isn't a good explanation, so we must wait and hope that somebody comes up with a better one.' I can't help feeling that such a position, though logically sound, would have left one feeling pretty unsatisfied, and that although atheism might have been logically tenable before Darwin, Darwin made it possible to be an intellectually fulfilled atheist

Richard Dawkins
Another curious aspect of the theory of evolution is that everybody thinks he understand it. I mean philosophers, social scientists, and so on. While in fact very few people understand it, actually as it stands, even as it stood when Darwin expressed it, and even less as we now may be able to understand it in biology.

Jacques Monod
The false view of evolution as a process of global optimizing has been applied literally by engineers who, taken in by a mistaken metaphor, have attempted to find globally optimal solutions to design problems by writing programs that model evolution by natural selection.